Influenza (the flu) is an illness that is caused by a virus that can make you feel very sick.

Every year in the United States, influenza infections occur during the fall and winter months. When a large number of people get the flu, this is called a flu epidemic. Influenza infections also occur at other times of year, at lower levels.

Influenza spreads easily between people; it is very contagious. It can spread from person to person in droplets created by coughing and sneezing. It can also be spread when people cough or sneeze into their hands, and then touch things.

Anyone can get the flu. However, some people can get much sicker. The young, the elderly and people with chronic lung diseases, like cystic fibrosis, or heart conditions can get very sick from the flu.

In people with CF, influenza can lead to a severe lung infection. If you have the flu, you will have many of the symptoms listed above.

Most likely, you will feel worse than you do with your usual lung infection or pulmonary exacerbation. It is very important to let your CF care center know as soon as possible if you have flu-like symptoms.

Antiviral medications are available to treat people when they get the flu. They are most effective if taken within 24 hours of the start of symptoms. It is important to contact your CF care center or doctor as soon as you feel flu-like symptoms to get these medicines. These drugs may help lessen your symptoms or how long you are ill. They do not prevent you from getting the flu.

Experts in CF and immunizations have developed the following guidelines to help prevent the flu:

Get vaccinated — Each year in the fall and winter the influenza vaccination, or "flu shot," is given to people with CF, their family members and their health care providers. This helps prevent the flu by helping the body fight off or increase its immunity to the current types of the flu virus.

The close contacts of people with CF should also get a flu shot. This will help protect people with CF from the flu. The fall season is the best time to get vaccinated, but getting vaccinated in December or January is still helpful as flu season can last until the spring.

Flu vaccine spray (e.g. FluMist®) — You may have heard about the “flu vaccine spray.” This vaccine is sprayed into the nose. It is only approved for people ages 2 to 49 years who do not have a lung disease, like CF or asthma.

However, family members without CF or other health conditions may be able to get the “flu vaccine spray.”

Practice good health habits — Infection control measures can help stop the spread of flu. These habits include:

Clean your hands — Clean your hands often with soap and water or with a 60 percent alcohol-based hand gel (especially after coughing or sneezing). This will help protect you and others around you.

Stop the spread — Cover your mouth and nose with a tissue when coughing or sneezing. Discard the tissue into a waste basket or covered container. Make sure you clean your hands afterward to prevent spreading germs to others.

Don’t touch — Limit touching your eyes, nose or mouth. Germs are often spread when a person touches something that has germs and then touches his or her eyes, nose or mouth.

Stay home — If you are sick, just stay home. You will help prevent others from becoming sick.

Keep your distance — Avoid close contact with people who are sick (stay at least 3 feet or an arm’s length away). When you are sick, keep your distance from others to protect them from getting sick.

The flu shot does not give you the flu, because the viruses in the flu shot are killed (inactivated). The risk of the flu shot causing serious harm is very small. However, like any vaccine, you could have mild side effects such as soreness, redness or swelling where the shot was given, a low grade fever or some mild aches. If these problems happen, they will begin shortly after the shot and usually last 1-2 days. If you are allergic to eggs, talk with your doctor about other ways to get the flu vaccine.

A pandemic is a disease outbreak that occurs around the world. A flu pandemic occurs if a new flu strain emerges for which people have little or no immunity and for which there is no available vaccine. Thus, a flu pandemic could spread easily from person to person and cause serious illness in many people in many countries in a very short time.